CN116620393A

CN116620393A - hydraulic steering unit

Info

Publication number: CN116620393A
Application number: CN202211554664.3A
Authority: CN
Inventors: 本特·波尔斯克罗
Original assignee: Sauer Danfoss ApS
Current assignee: Danfoss Power Solutions ApS
Priority date: 2022-02-18
Filing date: 2022-12-05
Publication date: 2023-08-22
Also published as: EP4230504A1; EP4230504B1; US20230264736A1

Abstract

A hydraulic steering unit is described, comprising: a supply port device having a supply port and a return port; a work port device having two work ports; a steering valve device having two valve elements which are arranged in a housing and which are movable relative to each other to change a characteristic of an orifice; and a measuring motor arranged in a line between the diverter valve assembly and one of the work ports. The hydraulic steering unit should create a similar end stop feel in both steering directions. For this purpose, a back pressure device is provided which generates a back pressure on the measuring motor, wherein the back pressure device is controlled by a valve element, and a friction device is provided between one of the valve elements and the housing or between the rotating part of the measuring motor and the housing, respectively.

Description

Hydraulic steering unit

Technical Field

The present invention relates to a hydraulic steering unit comprising: a supply port device having a supply port and a return port; a work port device having two work ports; a diverter valve device disposed between the supply port device and the work port device and having two valve elements disposed in the housing and movable relative to each other to change an area characteristic of the orifice; and a measurement motor disposed in a line between the diverter valve assembly and one of the work ports.

Background

Steering units of this kind are known, for example, from EP 3 078 571 B1 or US 10 723 378 B2.

The hydraulic steering unit provides a very accurate and comfortable steering when the measuring motor is arranged in the working line, i.e. in the line between the steering valve device and the working port. Dead band (dead band) between actuation of the steering wheel and reaction of the steered wheels can be minimized.

However, there arises a problem that the end stop feel in the steering wheel (or any other steering command device) will be different for the two steering directions. When the steering motor connected to the work port device reaches the end position on one side, the driver of the vehicle equipped with the hydraulic steering unit will feel a rather hard end stop, since the pressure of the fluid in the work line will increase and the steering motor is in the end position such that the steering motor can no longer rotate. On the other side, the end stop will not be too hard, since the outlet of the measuring motor is connected to the return line and from there to the tank.

Disclosure of Invention

The object of the invention is to create a similar end stop feel in both steering directions.

This object is solved in a hydraulic steering unit as initially described, wherein a back pressure device is provided which generates a back pressure on the measuring motor, wherein the back pressure device is controlled by the valve elements, and a friction device is provided between one of the valve elements and the housing, or between a rotating part of the measuring motor and the housing, respectively.

In this way, an elevated pressure can be created at the outlet side of the measuring motor, so that the measuring motor is no longer in operation when the end stop position of the steering motor is reached. Since the back pressure means is controlled by the valve elements, this requires that the two valve elements move relative to each other in order to change the characteristics of some orifices. However, in some cases, when the driver rotates the steering wheel, no movement of the two valve elements relative to each other occurs. For example, when a measurement motor is arranged in the working line connecting the valve device and the right working port, and the steering wheel has been actuated to move the steering motor to the left end stroke, and then rotate the steering wheel back to the neutral position, and again slowly rotate to the left hand side, a steering passing phenomenon may be found: rotating the steering wheel at a low rotational speed, e.g. up to 10rpm (revolutions per minute), will not cause the two valve elements to move relative to each other, and hydraulic fluid from the left working port can flow back to the return port without causing a significant increase in the pressure acting on the measurement motor.

However, when the friction device acts on one of the valve elements but not the other valve element, the friction force generated by the friction device holds the one valve element in place so that the other valve element can move relative to the first designated valve element. In this way, the back pressure device can create the desired back pressure.

In an embodiment of the invention, one of the valve elements is a spool valve actuated by a steering command device and the other valve element is a sleeve surrounding the spool valve, wherein the friction means acts on the sleeve. The friction means holds the sleeve in place, i.e. does not allow the sleeve to rotate, while the slide valve is rotated by a steering command device (e.g. a steering wheel). Therefore, even when the spool valve rotates only at a low rotational speed, the characteristics of the orifice between the spool valve and the sleeve change, so that a desired back pressure is generated.

In an embodiment of the invention, the spool valve and the sleeve are connected by neutral spring means, wherein the friction means generates a holding torque which is greater than the torque of the neutral spring means in a predetermined rotation angle between the spool valve and the sleeve. In particular, when the spool valve is fully deflected relative to the sleeve, the torque produced by the friction device is greater than the torque produced by the neutral spring device. Thus, even if the spool valve rotates as much as possible with respect to the sleeve, the sleeve is held in place so that the orifice for creating the back pressure can be fully opened or closed, which is required for the back pressure device.

In an embodiment of the invention, the sleeve is connected to the measuring motor and the friction means generates a holding torque which is smaller than the torque generated by the measuring motor. The sleeve can be returned to a neutral position relative to the spool valve despite the friction force generated by the friction device.

In an embodiment of the invention, the friction means comprise a compressed elastic element located between the sleeve and the housing and/or between the rotating element of the measuring motor and the housing. The elastic element may be, for example, a spring device or any other compressible element that generates a force that acts between the sleeve and/or the rotating element of the measuring motor and the housing, respectively. When the spool rotates, this force creates friction between the sleeve and the housing, which holds the sleeve in place.

In an embodiment of the invention, the elastic element is arranged in front of the sleeve or in front of the rotary element, respectively. In this position, there is enough room for accommodating the resilient element so that the structure of a conventional steering unit does not have to be significantly changed.

In an embodiment of the invention, a slip ring is arranged between the elastic element and the housing. The slip ring avoids wear of the elastic element.

In an embodiment of the invention, the slip ring is made of metal, hard plastic or polytetrafluoroethylene. The ring is pressed against the housing by means of the elastic element and thereby generates the required friction between the sleeve and the housing.

In an embodiment of the invention, the elastic element is in the form of an O-ring. For example, the O-ring is arranged in the groove and is compressed when the corresponding sleeve or the rotating element of the measuring motor is mounted to the housing. The compressed O-ring generates the necessary force for generating the required friction.

Alternatively or additionally, the friction means comprises a pressure chamber connected to the supply port, wherein the pressure in the pressure chamber acts radially and asymmetrically on the sleeve. When the pressure of the supply port acts asymmetrically and radially on the sleeve, the sleeve itself is pressed against the wall of the bore in the housing in which the sleeve is arranged. This is another possibility to create increased friction.

In an embodiment of the invention, the back pressure device comprises in the valve device a return orifice between the measuring motor and the return port, and a variable orifice connected to the supply port and to a point between the return orifice and the measuring motor. The variable orifice will only open when the spool valve has rotated beyond a predetermined angle relative to the sleeve, particularly when the spool valve has fully deflected. In this case, the variable orifice allows pressure from the supply port to reach the outlet of the measurement motor so that the desired back pressure is generated.

In an embodiment of the present invention, the return orifice is a fixed orifice. The fixed orifice does not change its characteristics during operation of the steering unit.

Drawings

The invention will now be described with reference to the accompanying drawings, in which:

FIG. 1 is a schematic illustration of a hydraulic steering system;

FIG. 2 shows orifices formed by the valve arrangement of the steering unit for three different steering situations;

FIG. 3 illustrates the steering system of FIG. 1 in a left end stroke position;

fig. 4 shows detail IV of fig. 3;

fig. 5 schematically shows a steering unit of the steering system in a cross-sectional view; and

fig. 6 shows the relief hole characteristics of some orifices of the valve arrangement.

Detailed Description

Like elements are denoted by like reference numerals throughout the drawings.

Fig. 1 shows a steering system 1 comprising a steering unit 2 and a steering motor 3. The steering unit 2 comprises a supply port arrangement having a supply port P and a return port T. Furthermore, the steering unit 2 comprises a load sensing port LS.

The steering unit 2 is connected to a pilot valve (priority valve) 4. The pilot valve 4 is connected to a pump 5, which pump 5 is driven by a prime mover 6 of the vehicle to be steered by the steering system 1.

The pilot valve 4 comprises a pilot port CF connected to the supply port P of the steering unit 2 and an auxiliary port EF connected to other hydraulic consumers in a manner not shown. The pilot valve 4 comprises a valve element 7, the position of which valve element 7 is controlled by means of the pressure at the load sensing port LS.

The steering unit 2 comprises a valve device 8 and a measuring motor 9.

Fig. 1 shows the valve device 8 in a position in which the pump 5 is running and not turning, i.e. the valve device 8 is in a neutral position. The valve device 8 is connected to a steering column 10, which steering column 10 can be rotated, for example, by means of a steering wheel (not shown).

The steering unit 2 comprises an inlet check valve 11 in an LS line 12 (i.e. a line connecting the LS port LS and the valve arrangement 8). Furthermore, the steering unit comprises an inlet check valve 13 in a pressure line 14 connecting the supply port P and the valve device 8. A pilot relief valve (pilot reduction valve) 15 is arranged between the LS line 12 and a tank line 16, which tank line 16 is connected to the valve device 8 by means of a valve 17. The valve 15 controls the maximum steering pressure (P-T) at the end stroke of the steering motor 3 by limiting the pressure in the LS line 12 from the pilot valve 4. The valve 17 is controlled by the pressure in the pressure line 14. When the pressure in the pressure line 14 exceeds the pressure in the tank line 16 by more than, for example, 5 bar, the valve 17 opens for returning oil from the valve means 8 to the tank 28. When the pressure difference drops below 5 bar, the valve 17 is closed for returning oil from the valve means 8. Then, in a so-called emergency steering mode, the returned oil is guided through the check valve 19 into the valve device 8 and then flows out to the steering motor 3. In the emergency steering mode, the measurement motor 9 acts as a manual pump driven by the steering wheel. Suction valves 20, 21 in the form of check valves are arranged between the left working line 22 and the tank line 16 and between the right working line 23 and the tank line 16, respectively. The left working line 22 connects the valve means 8 and the left working port L, while the right working line 23 connects the right working port R and the valve means 8.

The steering motor 3 comprises a rod 24 connected to a piston 25. The steering motor 3 includes a left working chamber 26 and a right working chamber 27. The left working chamber 26 is connected to the left working port L, and the right working chamber 27 is connected to the right working port R.

The valve arrangement comprises a plurality of orifices (orifices) or bleed holes (bleeds), some of which are illustrated in fig. 2. The valve device 8 comprises a fixed orifice a10, which fixed orifice a10 is connected to a tank line 16 via a emergency steering valve 17. Furthermore, the valve device 8 comprises a bleed hole a13/14, which bleed hole a13/14 connects the pressure line 14 and a point between the fixed orifice a10 and the measuring motor 9, as explained below. The orifice A13/14 may be implemented by a single orifice. However, due to structural constraints, the orifice A13/14 is realized by two orifices. The orifices A13/14 will be explained later.

Fig. 1 shows the steering system 1 in a neutral position, in which the piston 25 of the steering motor 3 is in its neutral position, so that the steered wheels of the vehicle to be steered by the steering system are driven straight ahead. When the pump 5 is running, the pilot valve 4 will direct the main flow out of the auxiliary port EF and into the tank 28. The restricted flow will flow to the LS port LS of the steering unit 2 such that the check valve 11 is opened and hydraulic fluid flows to the valve arrangement 8, further through the emergency steering valve 17 and to the tank 28 via the tank line 16.

When the steering motor 3 is actuated to steer the vehicle to the right hand side, the right pressure chamber 27 is pressurized via the right work port R. In this case, the valve device 8 connects the pressure line 14 to the measuring motor 9 and connects the measuring motor 9 to the right working port R. Hydraulic fluid discharged from the left working chamber 26 is led back to the valve device 8 and reaches the emergency steering valve 17 through the fixed orifice a 10. Since the emergency steering valve 17 is actuated in the opening direction by the pressure at the supply port P via the signal line 29, the emergency steering valve 17 is opened. Accordingly, hydraulic fluid discharged from left working chamber 26 is directed back to tank 28 via tank line 16.

When the piston 25 of the steering motor 3 reaches the right end stroke and cannot move further, it is impossible to supply hydraulic fluid further to the right working chamber 27, so that the pressure in the right working chamber 27 increases. The increased pressure is fed back to the outlet of the measuring motor 9. When the pressure balance across the measuring motor 9 is measured, the measuring motor 9 is no longer rotating. When the steering wheel can no longer be rotated, the driver is subjected to this situation. In the right end stroke, the driver experiences a hard end stop.

However, when the steering motor 3 is turned in the left end stroke, as shown in fig. 3, the situation is different.

In fig. 4, some throttle openings of the valve device 8 are shown. The pressure from the supply port P is directed to the left working line 22 and then from the left working line 22 to the left working port L. Hydraulic fluid discharged from the right working chamber 27 of the steering motor 3 is led back to the measuring motor 9. These fluids pass through the measuring motor 9 and are then led to the tank line 16 via the fixed orifice a10 and the emergency steering valve 17. Without any additional measures, there is no substantial pressure at the outlet of the measuring motor 9 (as shown in fig. 3, the right-hand side of the measuring motor 9), so that the driver is not subjected to a hard end stroke of the steering motor 3.

This is especially the case when the steering wheel is rotated to the left until the steering motor 3 reaches the left end stroke and again rotates back to the neutral position and then slowly rotates to the left. In this case, a steering through phenomenon (steer through phenomenon) may be found: rotating the steering wheel at a low rotational speed, for example up to 10rpm (revolutions per minute), will not cause any significant torque drag. Will be explained with reference to fig. 5 and 6.

Fig. 5 schematically shows a cross-section of the steering unit 2. The steering unit 2 includes a housing 30. The housing 30 includes a bore 31. A set of slide valves (spiols) 32 and sleeves 33 are arranged in the bore 31. The slide valve 32 comprises a connection geometry 34 by means of which the slide valve 32 can be connected to the steering column 10 of the steering wheel.

The spool valve 32 and the sleeve 33 are connected by means of a neutral spring sleeve 35.

The measuring motor 9 comprises a gear ring 36 and a gear 37. The distributor plate 38 is arranged between the housing 30 and the measuring motor 9. The measuring motor 9 is provided with an end cap 39 on the side opposite the housing 30. For purposes of this illustration, the distributor plate 38 and end cap 39 are considered to be part of the housing.

The universal joint shaft 40 connects the gear 37 and the sleeve 33 by means of a cross pin 41. The bearing set 42 is disposed between the housing 30 and the front face of the sleeve 33, and is spaced from the front face of the spool valve 32.

Friction means 43 are arranged between sleeve 33 and distributor plate 38, or (alternatively or additionally) between gear 37 and end cap 39. Friction means may also be arranged between the gear wheel 37 and the distributor plate 38. In any case, the friction means 43 are arranged between the rotating part of the steering unit 2, which is not connected to the steering wheel, and the housing 30, 38, 39.

In the present example, the friction means 43 are arranged between the front of the rotating parts 33, 37 and the housings 30, 38, 39.

The friction means 43 comprise a compressed elastic element 44, for example in the form of an O-ring, and a slip ring 45, which slip ring 45 is located between the elastic element 44 and the housing part 38 or 39. The slip ring 45 prevents wear of the elastic element 44. Only a small amount of compression of the O-ring is required.

Additionally or alternatively, the friction means 43' comprises a pressure chamber 46, which pressure chamber 46 is loaded by the pressure of the supply port P and has an additional opening 47, wherein the pressure of the supply port P can act asymmetrically and radially on the sleeve 33.

When the spool valve 32 rotates at a low rotation speed, the friction device 43 including the elastic member 44 or the friction device 43' using the pressure at the supply port P can both prevent the rotation of the sleeve 33. In the fully deflected position of the slide valve 32 relative to the sleeve 33, the friction device 43 generates a holding torque on the sleeve 33 that is greater than the torque of the neutral spring device 35. However, the holding torque produced by the friction means 43, 43' is smaller than the torque produced by the measuring motor 9.

The orifice A13/14 is formed by the spool valve 32 and the sleeve 33. As shown in FIG. 6, orifice A13/14 will only open when spool valve 32 has been rotated a large angle relative to sleeve 33, and in particular orifice A13/14 will only open when spool valve 32 has been rotated as far as possible relative to sleeve 33. The possible rotation is limited by the cross pin 41 penetrating the opening 47 in the spool valve 32, wherein the opening 47 has a larger diameter than the diameter of the cross pin 41.

When the steering motor 3 reaches the left end position, as shown in fig. 3, the orifice a13/14 is opened so that the flow from the supply port P reaches a point between the fixed orifice a10 and the measurement motor 9. In this way, the measuring motor 9 is subjected to an increased pressure in the left end position of the steering motor 3, so that the user is subjected to a hard end stroke.

This is the case even if the steering wheel is only slowly rotated. The friction means 43, 43' ensure that even in this operating mode the slide valve 32 can be rotated relative to the sleeve 33 so that the throttle bore a13/14 is opened.

Fig. 6 shows the relief hole characteristics of other orifices. It can be seen that orifice a10 is a fixed orifice. Other orifices such as the primary orifice A1 and the measurement motor orifice A2R, A3R, A2L, A L have conventional characteristics.

Claims

1. A hydraulic steering unit (2), comprising: a supply port device having a supply port (P) and a return port (T); a work port device having two work ports (L, R); a diverter valve device (8) arranged between the supply port device and the working port device and having two valve elements (32, 33) arranged in a housing (30, 38, 39) and movable relative to each other to change the area characteristics of an orifice (a 13/14); and a measuring motor (9) arranged in a line between the diverter valve arrangement (8) and one of the working ports (L, R),

characterized in that a back pressure device is provided which generates a back pressure on the measuring motor (9), wherein the back pressure device is controlled by the valve elements (32, 33), and friction devices (43, 43') are provided between one of the valve elements (33) and the housing (30, 38, 39) or between a rotating part of the measuring motor (9) and the housing (30, 38, 39), respectively.

2. A hydraulic steering unit according to claim 1, characterized in that one of the valve elements is a spool valve (32) actuated by a steering command device and the other valve element is a sleeve (33) surrounding the spool valve (32), wherein the friction means (43, 43') acts on the sleeve (33).

3. Hydraulic steering unit according to claim 2, characterized in that the spool valve (32) and the sleeve (33) are connected by neutral spring means (35), wherein the friction means (43, 43') generate a holding torque which is greater than the torque of the neutral spring means (35) in a predetermined rotation angle between the spool valve (32) and the sleeve (33).

4. A hydraulic steering unit according to claim 3, characterized in that the sleeve (33) is connected to the measuring motor (9) and the friction means (43, 43') generate a holding torque which is smaller than the torque generated by the measuring motor (9).

5. Hydraulic steering unit according to any one of claims 1 to 4, characterized in that the friction means (43, 43') comprise a compressed elastic element (44) located between the sleeve (33) and the housing (30, 38, 39) and/or between a rotating element (37) of the measuring motor and the housing (30, 38, 39).

6. Hydraulic steering unit according to claim 5, characterized in that the elastic element (44) is arranged in front of the sleeve (33) or in front of the rotating element (37), respectively.

7. The hydraulic steering unit according to claim 5 or 6, characterized in that: a slip ring (45) is arranged between the elastic element (44) and the housing (30, 38, 39).

8. Hydraulic steering unit according to claim 7, characterized in that the slip ring (45) is made of metal, hard plastic or polytetrafluoroethylene.

9. Hydraulic steering unit according to any one of claims 5 to 8, characterized in that the elastic element (44) is in the form of an O-ring.

10. Hydraulic steering unit according to any one of claims 1 to 9, characterized in that the friction means (43, 43') comprise a pressure chamber (46) connected to the supply port (P), wherein the pressure in the pressure chamber (46) acts radially and asymmetrically on the sleeve (33).

11. The hydraulic steering unit according to any one of claims 1 to 10, characterized in that the back pressure device comprises in the valve device (8) a return orifice (a 10) between the measuring motor (9) and the tank port (T), and a variable orifice (a 13/14) connected to the supply port (P) and to a point between the return orifice (a 10) and the measuring motor (9).

12. The hydraulic steering unit according to claim 11, characterized in that the return orifice (a 10) is a fixed orifice.